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// ownership. LinDB licenses this file to you under
// the Apache License, Version 2.0 (the "License"); you may
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// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing,
// software distributed under the License is distributed on an
// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
// KIND, either express or implied.  See the License for the
// specific language governing permissions and limitations
// under the License.

package lockers

import (
	"runtime"
	"sync/atomic"
)

// SpinLock implements sync/Locker, default 0 indicates an unlocked spinLock.
type SpinLock struct {
	_flag uint32
}

// Lock locks spinLock. If the lock is locked before, the caller will be blocked until unlocked.
func (sl *SpinLock) Lock() {
	for !sl.TryLock() {
		runtime.Gosched() // allow other goroutines to do stuff.
	}
}

// Unlock unlocks spinLock, this operation is reentrant。
func (sl *SpinLock) Unlock() {
	atomic.StoreUint32(&sl._flag, 0)
}

// TryLock will try to lock spinLock and return whether it succeed or not without blocking.
func (sl *SpinLock) TryLock() bool {
	return atomic.CompareAndSwapUint32(&sl._flag, 0, 1)
}
